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Trout can tolerate river's poisons

Thursday, August 01, 2013

The Cornishman

A RIVER so heavily polluted with toxins that it would kill most fish has been shown to support a population of brown trout.

The Hayle River, where heavy metals from the tin mining industry were carried out to sea, is among the most contaminated waterways in Britain, despite being an RSPB nature reserve.

The heavily polluted Hayle River which supports a population of gene-changing brown trout.

New research from the University of Exeter and Kings College London has shown brown trout can survive in the river despite the high metal concentrations.

Eduarda Santos, one of the Exeter researchers, said it was being put down to changes in the expression of their genes.

He said: "The story of the brown trout is a fascinating one, demonstrating its resilience and its ability to defeat the odds and tolerate the challenges imposed upon them as a result of human activities. Many aspects of this story remain untold, however.

"We do not know how or when this tolerance arose or what the future holds for them if challenged with further stressors in their environment.

"But we know that such populations need careful management. If the Hayle brown trout, with their unique physiology, were to be lost, it is possible this river may never be home to brown trout again.

"Understanding the relationship of fish with their environment is crucial to effectively managing and protecting our aquatic ecosystems."

Tamsyn Uren Webster, from Exeter University, said: "The work demonstrates that this population of brown trout has developed strategies for dealing with the metal pollution in the water and accumulation in their tissues, avoiding the lethal damage that such concentrations of metals would normally cause."

The researchers compared the trout with a population in a relatively clean site in the River Teign in Devon.

Results showed the accumulation of metals in the kidney and liver – where metals are stored and detoxified – were 19 and 34 times higher in the Hayle trout, respectively. In the gill, concentrations averaged 63 times higher in the Hayle fish.

The team believed a detailed understanding of how the Hayle trout population has developed this tolerance could have potential implications for restocking rivers.